Volumetric mass transfer coefficient, k(L)a, bubble size, and interfacial area were investigated in an aerated coaxial mixing system with an aspect ratio of 1.25 furnished with two central impellers and an anchor. The simplified dynamic pressure method and a combination of the dynamic gas disengagement and electrical resistance tomography methods were utilized for measuring k(L)a and bubble sizes, respectively. Carboxymethyl cellulose (CMC) solutions were used as the power-law non-Newtonian fluids. New correlations for the prediction of k(L)a in aerated coaxial mixing systems containing non-Newtonian solutions were developed. The pitched blade impeller in downward pumping generated the highest mass transfer and interfacial area and smaller bubble sizes at all anchor speeds and concentrations of the CMC solution. The anchor speed had a positive impact on the oxygen mass transfer up to 20 rpm. Bubble stability increased while the interfacial area decreased with an increase in the fluid apparent viscosity.